Progressive coding of information with progressively coded side information

A generalized progressive coding problem is introduced. Two correlated sources X and Y are coded in two stages. The first stage is the same as "sequential coding of correlated sources" in literature. At the second stage, Y₂ encoder refines the information of Y, and X₂ encoder, obtaining the output of both Y encoders, refines X. This problem provides some theoretical basis for progressive video coding. The achievable region of such problem is given. The minimum total rate at each stage is analyzed